Atomic contributions to ZnO mechanical properties at negative and positive pressures

The energy-volume curve of a crystalline solid is critically examined in terms of the mechanical contributions of its constituent atoms. In addition to the usual analysis in the positive compression regime, our computational approach covers the tensile behavior in the negative pressure region up to the spinodal stability limit. Using the rich polymorphism of ZnO as a test-bed example, we propose two atomic decomposition schemes that are able to recover the bulk moduli and the critical strengths of four ZnO phases providing an intriguing interpretation of the chemical bonding network as a parallel circuit of mechanical resistors. Our scheme also allows the identification of the role played by the cation and anion in the densification of the high-pressure polymorphs and up to the material rupture points. This approach may help in the quest for tailored materials with outstanding mechanical performance.